PO line item updation is erroring out stating "provide unique value for line number".

Summary:

For an already created PO (open) with line items. Line item updation is erroring out stating "provide unique value for line number" even after providing the exact line number of the items to be updated.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

25A

Code Snippet (add any code snippets that support your topic, if applicable):